Stethomostus

• previous
 
• next

Taxonomy

Family: Tenthredinidae
Family common name: common sawflies
Subfamily: Blennocampinae
Tribe: Phymatocerini
Genus: Stethomostus Benson, 1939
Subgenera: none

Background

The Tenthredinidae are the most species-rich family and are found throughout the world, in all continents but Antarctica. They are known as the “common sawflies.” They can generally be recognized by a cylindrical body and long, segmented antennae. Otherwise, they come in a variety of colors, sizes, and forms (Goulet 1992).

Sawflies in the subfamily Blennocampinae have a diverse set of life histories and habits. Many species are restricted to subtropical and tropical regions, but the genus is still fairly species-rich in North America. Blennocampinae includes many sawflies that feed on ornamental and forestry crops. This subfamily can be recognized by wing venation and bidentate mandibles (Smith 1969d).

Stethomostus is monotypic in North America. Stethomostus fuliginosus is about 6–6.5 mm in length and entirely black with white markings on fore tibia and partially darkened wings (Smith 1969d).

Diversity

There are seven described extant species worldwide. One species occurs in North America (Taeger et al. 2018).

Diagnostic characteristics

Subfamily characters

• angle of intersection of fore wing veins Cu1 and 1m-cu between 120°–150° (Goulet 1992)
• fore wing veins M and 1m-cu parallel (Smith 1969d)
• fore wing veins 2A and 3A incomplete (Smith 1969d)

Genus characters

• short occipital ridge present near mandible; ridge lacking pits (Goulet 1992)
• pedicel longer than wide (Smith 1969d)
• third antennal segment length about 1.5X length of fourth segment (Goulet 1992)
• eighth antennal segment between 1.2X and 2.5X as long as wide (Goulet 1992)
• prepectus present, epicnemial furrow present (Smith 1969d)
• fore wing veins 2A and 3A straight (Goulet 1992)
• hind wing cell M absent (Smith 1969d)
• fore tibia with furcate spur (Smith 1969d)
• pulvilli on the first and second tarsomeres well developed (Goulet 1992)
• tarsal claw basal lobe absent (Goulet 1992)
• mesoscutellar appendage length about one-fifth the length of the mesoscutellum (Goulet 1992)

May be confused with

Stethomostus can be confused with similar species in the subfamily Blennocampinae. It can be distinguished from most other genera by the length of the third antennal segment, and from similar species in Eutomostethus by the furcate foretibial spur and the straight apex to veins 2A and 3A of fore wing (Smith 1969d, Goulet 1992).

Exotic pest species of concern

none

Host associations

Stethomostus fuliginosus feeds on species of Ranunculus (buttercup) (Goulet 1992).

Life history

unknown

Distribution

World: This genus is known from North America, throughout Europe and Russia, and in China, Japan, and Vietnam (Taeger et al. 2018).

North America: Stethomostus fuliginosus was introduced to North America and now occurs in northeastern United States, in New England west to the Great Lakes region, and into New Brunswick in Canada (Smith 1969d).

Map data from: GBIF.org (29 October 2019) GBIF Occurrence Download Stethomostus

Details about data used for maps can be found here.